Yeah, I always build the high-poly first and bake onto a low-poly. Easier to figure out what's going to bake onto what when you've got all the detail there.
Texturing, I just save the UV map out and paint it up in Photoshop. You can bake textures from procedural shaders in Maya (my main tool, for now) and work from that, but I prefer just painting it all by hand, preferably using a tablet. Unfortunately, the only one I have is an old Wacom ArtPad II from 1996, and my machine doesn't have a serial port anymore, so I'm stuck using a mouse.
You can actually paint directly onto the model, but I find the tools in Maya are too crude to do a good job there. I think many creature designers are using ZBrush to do exactly that (not sure though, I haven't researched what ZBrush does). For vehicles I find Photoshop works just fine though.
When it comes to reference art, I personally prefer to sketch out some orthographic drawings of the model myself, based on any reference I could find. This gives me a feel for the overall proportions of the beast, and lets me make decisions on what I have to do to get it to work in 3D. The Corsair, as an example, needed a folding ventral fin for the landing gear to make sense - I don't think the original design had landing in mind.